Five new trinuclear complexes with formula [(CuL
α−Me)
2Ce(NO
3)
3] (
1) and [(CuL
α−Me)
2Ln(H
2O)(NO
3)
2](NO
3)·2(CH
3OH) (Ln = Gd(
2), Tb(
3), Dy(
4) and Er(
5)) have been synthesized using the bidentate N
2O
2 donor metalloligand [CuL
α−Me] (H
2L
α−Me =
N,
N′-bis(α-methylsalicylidene)-1,3-propanediamine) and structurally characterized. In the case of compound
1, the larger ionic radius of Ce(III) leads to a neutral trinuclear complex with an asymmetric CeO
10 tetradecahedron coordination geometry formed by four oxygen atoms from two (CuL
α−Me) units and three bidentate NO
3− ligands. In contrast, the isomorphic complexes
2–
5, with smaller Ln(III) ions, give rise to monocationic trinuclear complexes with a non-coordinated nitrate as a counter ion. In these complexes, the Ln(III) ions show a LnO
9 tricapped trigonal prismatic coordination geometry with C
2 symmetry formed by four oxygen atoms from two (CuL
α−Me) units, two bidentate NO
3− ligands and a water molecule. The magnetic properties show the presence of weak antiferromagnetic interactions in
1 and weak ferromagnetic interactions in
2–
5. The fit of the magnetic properties of compounds
2–
5 to a simple isotropic-exchange symmetric trimer model, including the anisotropy of the Ln(III) ions, shows that in all cases the Cu-Ln magnetic coupling is weak (
JCu-Ln = 1.81, 1.27, 0.88 and 0.31 cm
−1 for
2–
5, respectively) and linearly decreases as the number of unpaired f electrons of the Ln(III) decreases. The value found in compound
2 nicely fits with the previously established correlation between the dihedral Cu–O–O–Gd angle and the
J value.
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